Adjusting mechanism between brake shaft and lever



p 6, 1949- K. B. MacDOUGALL 2,481,319

ADJUSTING MECHANISM BETWEEN BRAKE SHAFT AND LEVER Filed Aug. 19, 1947 2Sheets-Sheet l INVENTOR.

Sept. 6, 1949. MacDOUGALL 2,481,319

ADJUSTING MECHANISM BETWEEN BRAKE SHAFT AND LEVER Filed Aug. 19, 1947 2Sheets-Sheet 2 A .l/JI-J; r"

IN VEN TOR.

ATTORNEYJ Patented Sept. 6, 1949 OFFICE ADJUSTING MECHANISM BETWEENBRAKE SHAFT AND LEVER Kirkland B. MacDougall, Benton, Pa.

Application August 19, 1947, Serial No. 769,393

2 Claims. (Cl. 188-495) This invention relates to motor vehicle brakes,and more particularly to a. mechanism for providing adjustment of thebrakes automatically as the brake lining wears.

Some of the patents oi the prior art have attempted to provide for theautomatic adjustment of brake mechanisms, notably the patents to Leon T.Freeman and Roy H. Shively, Patent 2,379,796; Patent 2,385,621;andPatent 2,385,622. Generally, these patents provide a ratchet gear foroperating the cam shaft of a brake mechanism. The inherentcharacteristics of the'prior art brake adjustment mechanisms are suchthat while they operate quite satisfactorily under certain conditions,the unfailing proper operation of the brake mechanism is not positivelyassured. For instance, in the arrangement and disposition of the ratchetgear and the other component elements that are within the housing of thebrake adjustment mechanism, the fact was not taken into considerationthat if the ratchet gear became totally disengaged from the otherelements with which it cooperates the brakes of the vehicle would bereleased and, of course, this might result in serious accidents.

In my invention I overcome the possibility of the ratchet gear beingtotally disconnected from the component elements with which itcooperates and, therefore, the possibility of accidental andunintentional release of the brakes is overcome. The arrangement anddisposition of my ratchet gear and other elements with which itcooperates within the casing or housing are such that the ratchet gearcannot possibly be disengaged from the two elements with which itcooperates and the structural features of the said elements are suchthat the ratchet gear, at any one'time or under any conditions, can onlybe disassociated from one of the elements, but never from both.

In my invention I provide certain mechanismv for automatic adjustment ofthe brakes as the brake lining wears. This mechanism includes a novelform of closure that is applied to one end of a substantiallycylindrical hollow casing wherein the component parts of the mechanismare positioned and which closure carries on its inner face, when inposition, a plurality of inclined teeth which are adapted to interfitand cooperate with similarly formed teeth on a ratchet gear, the teethon the ratchet gear being inclined oppositely to the teeth on the innerface of the closure. The mechanism within the hollowcasing includes anannular pawl in which coil springs are disposed in recesses and whichsprings exert their motive force against a gear 2 ring, the latter ofwhich has inclined teeth on a face thereof, which teeth engage similarlyformed teeth on another portion of the ratchet gear and which teeth onthe ratchet gear are opp y inclined with respect to the teeth on thegear ring.

When the closure plate carrying the gear teeth is properly removablysecured to the casing, sufficient compression has been placed on thesprings carried by the pawl and the tolerances between the pawl, thegear ring, the ratchet gear and the teeth on the face of the closure aresuch that these elements are capable of axial movement to allow them toeither clutch and engage each other, or to axially move with respect toone or more of the elements. This axial movement and the engagement ofthe gear teeth on the gear ring, the rotatable gear and the closure arethe means whereby the brakes of the vehicle are automatically adjustedwhen the brake lining of the braking system has become worn. So long asthe brake lining has not become worn the pawl, the gear ring and theratchet gear will, of course, function when the brakes are operated, butthese elements will rotate with respect to each other and not effect aslack take-up of the brake mechanism and will only take up the slack andautomatically adjust the brakes when the brake lining, brake bands orbrake locks have become worn.

Another aspect of my invention is the fact that I provide a safetyfeature wherein only one pair of the toothed members will disengage onany occasion and further that it is impossible to free the ratchet gearentirely, for if this ratchet gear were entirely freed, the brakes ofthe vehicle would be released.

It is a principal object of my invention to improve over the devices setforth in the prior patents.

Another object of my invention is to reduce the number of parts requiredfor this purpose, to not only reduce the cost of operation andmanufacture, but to reduce the size of the mechanism and to render theoperation saferand more eflicient.

Another object of my invention is to provide a device for automaticallyadjusting the brakes .of a vehicle as the brake lining wears andincluding a novel arrangement of interengaging and cooperating elements,one of which constitutes a closure plate for the casing within which thesaid elements are disposed.

Another object of my invention is to provide in a device forautomatically adjusting the brakes linother object of my invention is toprovide a device for automatically adjusting the brakes of a vehicle asthe brake lining wears, which in cludes a substantially cylindricalhollow casing with an integral extended arm, the said casing containingor having positioned therein the several toothed elements that cooperatewith each other and which elements are concentrically disposed aboutextensions in the form of a sleeve on which a ratchet gear is carriedand the peripheral dimensions of all of the elements being substantiallythe same and fitting closely within the interior walls of the casing,thus providing a very compact, durable and long lasting device which iseflicient in its purpose and operaton and requiring little, if any,manual adjustment or maintenance once the device has been installed onthe vehicle.

Other objects will appear to those skilled in the art from a reading ofthe following specification.

The accompanying drawings illustrate a preferred embodiment of theinvention, but it is understood that modifications may be made thereinwithout departing from the spirit of the invention as hereinafterclaimed.

Figure 1 represents a front elevation of the new and improvedbrake-adjusting mechanism.

Figure 2 is a horizontal section, taken on the line 2-2 of Figure 1.

Figure 3 is a front elevation of the operating arm of thebrake-adjusting mechanism, together with its casing, and showing certainof the component elements removed from the casing and showing the innerside of the pawl and the'extension of the bracket.

Figure 4 is a rear elevation of a component known as the closure platehaving the teeth integral therewith.

Figure 5 is a side elevational view of the closure plate shown in Figure4.

Figure 6 is a front elevation of the ratchet gear.

Figure 7 is an elevational view of a component known as a gear ring.

The device comprises a forged steel or other suitable hollow open endedcasing in having an integral operating arm II which extends laterallyfrom the exterior thereof. The operating arm II has an aperture l2 bymeans of which it may be connected to thebrake-operating rod of thevehicle. A ratchet gear I5 is positioned within the cylindrical case Inand is provided .with a series of splines H; by means of which it mayengage a complementary splined end of a cam shaft I! to actuate thebrake. The axis of the ratchet gear l5 coincides with that of the shaftl1, and when the brake-operating rod is operated about this axis, thecam shaft I! will be rotated to actuate the brakes.

Seated within the casing I0 is a circular pawl 20. As seen in Figure 2of the drawings, the pawl 20 is under cut at its bottom to accommodatean inwardly extending flange 2| at one open end of the casing in, sothat the pawl 20, while free to rotate about the axis of the casing l0and the ratchet gear l5, cannot move down-' wardly or outwardly beyondthe flange 2!. A

bracket 23 is generally circular or ring-like in outline, and has alateral extension 26' for attachment to the air chamber or other part ofthe vehicle. If desired, the extension 28 may be provided with a hole 21for the reception of a bolt which serves to fixedly secure the same to asuitable part of the vehicle.

The upper surface of the pawl 20 is provided with a plurality of spacedapertures 30, for a purpose to be described more particularlyhereinafter. The same surface of the pawl 20 is also provided with twodiametrically opposed elongated recesses 3 I. These recesses 3| aredesigned to receive the diametrically opposed projections 32 which areon the lower face or surface of an annular gear ring 33. The gear ring33 is positioned between the ratchet gear 15 and the pawl 20; A coilspring 35 is seated in each aperture 30 and the ends of said springs soseated project beyond the upper face or surface of the pawl 20 and exerttheir motive force so as to press the gear ring 33 against the ratchetgear l5. While six such apertures 30 and springs 35 are shown, it isapparent that a more or less number of apertures and springs may be usedas required.

Th ratchet gear is is integral with or amxed to an internal sleeve 31the ends of which sleeve projects beyond both toothed surfaces of theratchet gear [5. The splines l6 extend inwardly from at least a portionof the sleeve 31, The

pawl 20 and the gear ring 33 are concentrically disposed on one of theprojecting end portions of the sleeve 31, as indicated most clearly inFigure 2 of the drawings. The lower surface of the gear rin'g 331ssmooth, except for the projections 32, and the upper surface is providedwith inclined teeth for engagement with complementary inclined teeth onvthe under side of the ratchet gear l5 and which last mentioned teeth areinclined oppositely to the teeth on the upper surface of the gear ring33. These matching interfitting teeth are so arranged that the ratchetgear I5 will grip the gear ring 33 as it turns in one direction, but mayslide over the gear ring 33 in the opposite direction due to theopposite inclination of the teeth.

The upper surface of the ratchet gear I5 is provided with another seriesof inclined teeth, these teeth being oppositely inclined with respect tothe teeth on the lower surface of the ratchet gear I 5. The other endportion of the case II is preferably interiorly threaded at 39. Anexteriorly threaded closure plate 40 is adapted to engage the threads 39of the casing ill to maintain the ratchet gear IS, the gear ring 33, andthe springs 35 in place. A reduced lower surface of the closure plate40, in contact with the upper surface of the ratchet gear I5, isprovided with inclined teeth that are complementary to but oppositelyinclinedly disposed with respect to the upper teeth of the ratchet geari5, which results in gripping in one direction and sliding in theOpposite direction when operating arm Ii is moved.

In assembling the device, the pawl 20 is inserted 111,03 liLflrst, andthe bracket 23 is weldedthereto whereby a subassembly of the twocomponent elements results. Thereafter, the springs 35 are seatedin theapertures 30, then the gear ring 33 is positioned so thatthe-projections 32 enter the recesses in the pawl 3|, then the ratchetgear i5 is inserted, and then the closure plate 40 is screwed into thecase III to engage the threads 33' thereof. The whole device is flttedover the camshaft II, which engages the splines IS, on the ratchet gearl5, and which is held in place by means of a washer l2 and nut '43.

In the normal operation of the brakes and assuming that there has beenno wear of the brake bands and consequently no need for adiustment, thecomponent parts of the brake adluster are in the positions andrelationships as shown in Fig. 2 of the drawing. We will assume nowthat, with the brake adjuster applied to the vehicle by fixedly mountingthe bracket 26 to a suitable portion of the vehicle and that the arm ithas connected thereto the brake operating rod and the brakes are appliedin the normal way, the arm I i, as viewed in Fig. 1, will be movedclockwise and, of course, the casing, the gear ring, ratchet gearsplined to the cam shaft, and the ratchet closure plate, all move inunison and the extent of the rotative movement, where no wear of thebrake bands has taken place, is, of course, limited as the brakes, undersuch circumstances, are properly adjusted and there is no relativemovement of any of the aforesaid component parts,'either in applying orreleasing the brakes, as these parts, as aforesaid, move rotatably inunison.

We will assume now that wear of the brake bands has occurred and thatthe operator, under these circumstances, applies the brakes by actuatingthe same and consequently rotating arm ii in a clockwise direction, asseen in Fig. 1 of the drawings. The fact that the brake bands havebecome worn and, therefore, the necessity of taking up the slack, whenthe brakes are applied, will allow the arm ii to travel a greaterdistance in its rotative movement than in the aforesaid normal operationof the brakes where no wear has occurred and this greater rotativemovement of the arm along with the casing, the ratchet closure, the gearring, the ratchet gear splined to the cam shaft, will result in theengagement of the diametrically disposed projections 32 carried by thegear ring 33 with the side walls of the recesses 3i in the fixed pawl,thus stopping the rotative movement of the gear ring 33! and, as themeshed ratchet gear further rotatably moves, the teeth of the ratchetgear that are in engagement with the teeth of the gear ring will bedisengaged by axial movement of gear ring 33 which effects compressionof the springs '35 positioned between the pawl and the lower face of thegear ring. Then the ratchet gear, which is splined to the cam shaft,will rotatably move and move the cam shaft with it for at least thedistance of one tooth movement and then, by the expansive action ofsprings 35, the teeth of the ratchet gear will reengage the gear ringand, of course, as the ratchet gear moves, the closure plate with itsteeth in engagement with the teeth on the other face of the ratchet gearmoves in unison therewith. Now we have been talking about theapplication or actuation of the brakes to apply the same and the factthat the cam shaft for the actuation of the brakeshasbeenrotatablyinovedto a new position ofadjustment for proper functioningof the brakes; g After the-camshaft has been rotated :for at least onenotchof the gear'teeth on one face of the ratchet gear by disengagementof the teeth on the gear ring and one face of the'ratchet gear andsetting the brakes in the new position, the brakes, of course, must'bereleased. In the release of the brakes, thearm H moves counterclockwiseand, in doing so, the" teeth on the one face of the ratchet gear areinengagement with the teeth on the gearring'and, atthe outset, beforeactual release ofthe brakes, th teeth on the other face of the ratchetare in engagement with the teeth on the closure. On this return rotativemovement, which is started from an extreme forward position where thebrakes are actually adjusted, the arm H, of course, moves in the reversedirection from the brake applying direction and carries with it thecasing and the toothed closure. As the ratchet gear will be held in thenew position of adjustment by the teeth on the one face thereof being inengagement with the teeth on the gear ring33, the arm, casing, andclosure plate with its teeth will be moving rotatively the distance ofat least one tooth and the teeth on the closure plate will be disengagedfrom the teeth on the face of the ratchet gear, by axial displacement ofthe housing and. the closure plate, this axial movement being permittedby the space between the pawl and the.

gear ring. The ratchet gear is held stationary so that its teeth willthen reengage in the new position, with the teeth on the closure plateby means of the spring 35. It is understood that the brake shoes arespring loaded and consequently there is a force exerted to return thesame to a released condition, thus causing the cam shaft to rotate andcarry with it the ratchet gear to brake released condition. Thus thebrakes and the brake adjuster are again normal.

From the foregoing, it will be clearly seen that the operation of theparts briefly described consists in the normal operation of the brakesand the brake adjuster where no wear of the brake bands has taken place,the teeth on the opposite faces of the ratchet gear are in engagementrespectively with the teeth on the closure plate and the teeth on thegear ring and move in unison. Where wear of the brake bands takes place,and the brakes are actuated, the rotative movement of the ratchet gear,which is splined to the cam shaft, moves relatively to the gear ringwhich becomes fixed when the brakes are actuated and, when the brakesare then released after adjustment has occurred, the teeth carried bythe closure plate move relatively with respect to the ratchet gear whichis in a fixed position.

The interior dimension of the casing is such with respect to thetransverse thickness of the pawl, gear ring, ratchet gear and the teethon the closure plate, that a limited space is provided between the fixedpawl and the gear ring, such space being of a dimension only slightlygreater than the depth of the teeth. Thus it will be seen that thedisengagement of but only one pair of teeth at a time can possiblyoccur.

I claim:

1. In a self-adjusting brake mechanism, a hollow cylindrical casinghaving open opposite sides, an operating arm carried by the casing, aratchet gear having teeth on opposite sides thereof positioned withinthe casing, a sleeve of uniform diameter on which said ratchet gear isfixed between the ends thereof, a closure for one sideof the casinghaving teeth integral therewith, the said closure teeth being disposedinteriorly of one end portion of the casing concentrically with respectto the sleeve on one side of the ratchet gear and the teeth thereofbeing removably engageable with the teeth on one side of the ratchetgear, a gear ring having teeth on one face to removably engage the teethof the ratchet gear on the other side thereof, a pawl adjacent the gearring and concentric with the ratchet gear sleeve in the other endportion of the casing and having pawl means for inter-engagement withmeans on the other face of the gear ring, an integral shoulder on thecasing extending into the pawl, a bracket which acts as a closure forthe other side of the casing irremovably joined with the pawl on theopposite side of the shoulder, spring means held by the pawl forelastically urging the gear ring against the ratchet gear and the teethon the closure against the ratchet gear, and there being a space greaterthan a tooth depth and less than twice the tooth depth of all of thesaid mentioned teeth between the gear ring and the pawl which willprevent simultaneous disengagement of the ratchet gear teeth from theteeth on the closure and the teeth on the gear ring,

2. In a self-adjusting brake mechanism, a hollow cylindrical casinghaving open opposite sides, an operating arm carried by the casing, aratchet gear having teeth on opposite sides thereof positioned withinthe casing, a sleeve of uniform diameter on which said ratchet gear isfixed between theends thereof, a closure for one side of 8 the casinghaving teeth integral therewith, the said closure teeth being disposedinteriorly of one end portion of the casing concentrically with respectto the sleeve on one side of the ratchet gear and the teeth thereofbeing removably engageable with the teeth on one side of the ratchetgear, a gear ring having teeth on one face to removably engage the teethof the ratchet gear on the other side thereof, a pawl adjacent the gearring and concentric with the ratchet gearsleeve in the other end portionof the casing and having pawl means for interengagement with means onthe other face of the gear ring, a bracket which acts as a closure forthe other side of the casing irremovably joined with the pawl, springmeans held by the pawl for elastically urging the gear ring against theratchet gear and the teeth on th closure against the ratchet gear andthere being a space greater than a tooth depth and less than twice thetooth depth of all of the said mentioned teeth between the gear ring andthe pawl which will prevent simultaneous disengagement of the ratchetgear teeth from the teeth on the closure and th teeth on the gear ring.

KIRKLAND B. MACDOUGALL.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,755,525 Tatter Apr. 22, 19302,377,014 Keller May 29, 1945 2,385,621 Freeman et a1. Sept. 25, 19452,385,622 Freeman et al. Sept. 25, 1945

